mmu_context_32.c

/* * This file contains the routines for handling the MMU on those * PowerPC implementations where the MMU substantially follows the * architecture specification. This includes the 6xx, 7xx, 7xxx, * 8260, and POWER3 implementations but excludes the 8xx and 4xx. * -- paulus * * Derived from arch/ppc/mm/init.c: * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) * * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au) * and Cort Dougan (PReP) (cort@cs.nmt.edu) * Copyright (C) 1996 Paul Mackerras * * Derived from "arch/i386/mm/init.c" * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * */#include <linux/mm.h>#include <linux/init.h>#include <asm/mmu_context.h>#include <asm/tlbflush.h>unsignedlong next_mmu_context;
unsignedlong context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
#ifdef FEW_CONTEXTSatomic_t nr_free_contexts;
struct mm_struct *context_mm[LAST_CONTEXT+1];
void steal_context(void);
#endif /* FEW_CONTEXTS *//* * Initialize the context management stuff. */void __init
mmu_context_init(void)
{
/* * Some processors have too few contexts to reserve one for * init_mm, and require using context 0 for a normal task. * Other processors reserve the use of context zero for the kernel. * This code assumes FIRST_CONTEXT < 32. */
context_map[0] = (1 << FIRST_CONTEXT) - 1;
next_mmu_context = FIRST_CONTEXT;
#ifdef FEW_CONTEXTS atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1);
#endif /* FEW_CONTEXTS */
}
#ifdef FEW_CONTEXTS/* * Steal a context from a task that has one at the moment. * This is only used on 8xx and 4xx and we presently assume that * they don't do SMP. If they do then this will have to check * whether the MM we steal is in use. * We also assume that this is only used on systems that don't * use an MMU hash table - this is true for 8xx and 4xx. * This isn't an LRU system, it just frees up each context in * turn (sort-of pseudo-random replacement :). This would be the * place to implement an LRU scheme if anyone was motivated to do it. * -- paulus */void
steal_context(void)
{
struct mm_struct *mm;
/* free up context `next_mmu_context' *//* if we shouldn't free context 0, don't... */if (next_mmu_context < FIRST_CONTEXT)
next_mmu_context = FIRST_CONTEXT;
mm = context_mm[next_mmu_context];
flush_tlb_mm(mm);
destroy_context(mm);
}
#endif /* FEW_CONTEXTS */